1. Field
The disclosed concept pertains to vacuum switching apparatus such as, for example, vacuum switches including a vacuum envelope such as, for example, vacuum interrupters.
2. Background Information
Vacuum interrupters include separable main contacts disposed within an insulated and hermetically sealed vacuum chamber. The vacuum chamber typically includes, for example and without limitation, a number of sections of ceramics (e.g., without limitation, a number of tubular ceramic portions) for electrical insulation capped by a number of end members (e.g., without limitation, metal components, such as metal end plates; end caps; seal cups) to form an envelope in which a partial vacuum may be drawn. The example ceramic section is typically cylindrical; however, other suitable cross-sectional shapes may be used. Two end members are typically employed. Where there are multiple ceramic sections, an internal center shield may be disposed between the example ceramic sections.
Typically, the number of sections of ceramics for electrical insulation are a number of solid opaque structures.
U.S. Pat. No. 4,408,107 discloses a vacuum envelope including a housing made of non-magnetic metallic material with end plates fabricated from insulating material in the form of a ceramic or crystallized glass.
U.S. Pat. No. 4,249,050 discloses a vacuum switch comprising a vacuum vessel defined by an insulating cylinder, which is preferably made of a transparent material such as glass, and end plates. A cylindrical member may be constructed by a metal cylinder which is provided with a glass window at a portion corresponding to a gap between shields to permit direct observation of the interior of the vacuum vessel.
U.S. Patent Application Pub. No. 2007/0278187 discloses a vacuum bottle attached to a housing to form a switch or interrupter assembly. The vacuum bottle contains a contact. An actuating element connects to an actuating mechanism for either a switch or interrupter. An indicator for the contact is attached to an insulated rod of the actuating mechanism. The indicator has a red portion (for indicating the contact is closed) and a green portion (for indicating the contact is open). A viewing window extends through the housing so that, when the actuating mechanism opens or closes the contact, the red portion or green portion of the indicator is aligned with the viewing window and shows the position of the contact.
U.S. Patent Application Pub. No. 2007/0295694 discloses a vacuum bottle with a viewing window that is mounted in series with a circuit breaker within a porcelain casing. A rigid tube and an elastomer casing are arranged to define an observation window that is at least translucent, and through which the open or closed position of switch contacts can be seen. The rigid tube is made by molding a plastics material that is transparent or at least translucent. The plastics material may be a transparent thermoplastic polymer such as safety glass.
There is room for improvement in electrical switching apparatus, such as vacuum switches.
There is also room for improvement in vacuum interrupters.